| Line 3 was replaced by line 3 |
| - !liquid Nitrogen |
| + !General Remarks |
| Lines 5-8 were replaced by lines 5-19 |
| - Most of our cryostats and cryo-magnets have an outer liquid nitrogen jacket to reduce the heat load on the helium bath. |
| - The storage dewars are prepared by the sample environment staff and can be picked up at the preparation area (between FOCUS and MARS). |
| - The dewars provided are self pressurizing systems with a mechanical level indicator at the top as shown below. |
| - [LN2_dewar_schematics|cl_clpb.gif] |
| + Handling cryogenic liquids should only be done by trained people. The following instruction are by no means a replacement for a certified cryogenics course. They are meant as a reference for how to handle cryogenics at the Neutron guide hall. \\ |
| + Fear is a bad teacher |
| + and you should always consult a more experienced instrument scientist or [the sample environment team|SampleEnvironment], |
| + if you are in doubt how to handle things correctly. \\ |
| + Please always keep in mind that you are working with boiling liquids which will evaporate rather quickly when exposed to ambient temperatures.\\ |
| + Think about the consequences of your doing __before__ you do it (e.g. what will happen if you open a specific valve). |
| + |
| + For information on how to set up an orange cryostat and how to change samples, please follow this link: [OrangeCryostat|http://lns00.psi.ch/sinqwiki/Wiki.jsp?page=OrangeCryostatCooldownProcedure]. |
| + |
| + !Liquid Nitrogen |
| + |
| + Most of our cryostats and cryo-magnets have an outer liquid nitrogen jacket to reduce the heat load on the helium bath.\\ |
| + The storage dewars are prepared by the sample environment staff and can be picked up at the preparation area (between FOCUS and MARS).\\ |
| + The dewars provided are self pressurizing systems with a mechanical level indicator at the top as shown below.\\ |
| + [LN2_dewar_schematics|LN2.png] |
| Lines 12-13 were replaced by lines 23-24 |
| - The filling hoses have a metallic protection sleeve. The valves and the hose get very cold during a nitrogen transfer. |
| - *Make sure that you wear protective leather gloves when handling cold parts. |
| + The filling hoses have a metallic protection sleeve. The valves and the hose get very cold during a nitrogen transfer. |
| + *Make sure that you wear protective leather gloves when handling cold parts, however the gloves should never be soaked with LN2 or LHe. |
| At line 14 added 1 line. |
| + |
| At line 17 added 10 lines. |
| + !Liquid Helium |
| + |
| + Liquid Helium dewars are provided by the sample environment staff at the preparation area.\\ |
| + At PSI we run a Helium recovery system. |
| + *Please make sure that the dewars are always connected to the recovery line when not in use |
| + *Remember to close the valve on the recovery line when taking a dewar away and to open it after return |
| + *The Level meter in the preparation area shows the level in litres. Make sure that there is sufficient helium for filling. The dewars |
| + should be returned with a level of at least 10-15 litres. |
| + *When using the crane be aware that no equipment (or dewar) should be moved over the DMC detector |
| + |
| Line 21 was replaced by lines 43-47 |
| - [He_gas_line|gasline.png] |
| + __Helium Dewar Transport:__\\ |
| + Helium dewars are brought into the experimental area with the 1T crane. |
| + *Only instructed people are allowed to use the crane. (A short training is offered by the LDM mechanics personal.) |
| + *Only dewars with pre-installed transport straps are allowed for crane transportation. |
| + *To extend the straps please use the proper extensions as shown in the picture below. |
| At line 22 added 1 line. |
| + | [transport extensions|HeDewartransport.png] | [dewar with transport fixtures|transportstraps.png] |
| Line 24 was replaced by lines 51-86 |
| - [CCU|CCU.png] |
| + |
| + __Helium Transfer:__ |
| + *Before you open the extraction port you should release the pressure in the dewar which might have built up during transport by opening one of the release valves |
| + *Insert the Helium siphon first into the transport dewar. |
| + *close all manual pressure release valves |
| + *slowly lower the siphon into the dewar and observe the pressure rise in the dewar (try to stay below 0.2bar) |
| + *you should see gas streaming out on the other end of the siphon |
| + *don't put your hands in the gas stream |
| + *when it starts to turn white you can insert this end into the cryostat Helium filling port |
| + *continue to lower the siphon into the transport dewar until you reach the bottom. |
| + *switch on the compressed Helium gas line and connect the gas hose to one of the pressure release valves |
| + and open it. The dewar is now pressurized to 0.15 bar over pressure. |
| + *make sure not to empty the vessel completely, the people running the liquefier will love you. On the transfer line, normally there is a prolongation with a hole at 10 cm above the end. If not, you should lift the transfer line by 10 cm after inserting. |
| + When the transfer is finished: |
| + |
| + *stop the pressure line |
| + *release the dewar pressure before you remove the siphon. |
| + *make sure that the extraction and filling ports are properly sealed. It might be necessary to |
| + use a hair dryer to remove the ice. |
| + |
| + [He_gas_line|gasline.png] |
| + |
| + !Returning Liquid Helium Dewars |
| + please return dewars to the dewar station as soon as possible after the transfer |
| + *connect the dewar to the rubber hose of the dewar station |
| + *open the manual valve to the recovery |
| + *open the manual pressure release that is connected to the recovery on the dewar |
| + *check the other manual pressure release. it MUST be closed |
| + *retighten the locking nut of the Helium extraction port |
| + *connect the level probe |
| + |
| + IMPORTANT: |
| + recheck that all valves are in the right state and the level is reading before you leave |
| + [afterfill.png] |
| + |
| + In case you are unsure about certain procedures, please contact sample environment staff |
LIN